Cell grouping is a well-known technique for improving and managing interference in cellular wireless communication networks. Already for 2 G wireless communication network planning (on rather long time horizon, days typically), inter-cell interference measurements are performed to group cells together, in order to minimize radio interference and make cell and/or frequency planning more efficient.
For future wireless communication networks, an important method to increase both coverage and capacity is to use cell cooperation for signal transmission and reception between nodes in the network and user equipments located in the cooperating cells. This is generally referred to as coordinated multipoint transmission and reception (CoMP). This cooperation can be used in downlink communication for scheduling and data transmission using, for example, beam forming or joint coherent processing and transmissions, or in uplink communication, where a multitude of antennas are used to suppress and cancel interference and increase the signal-to-noise (SNR) ratio. It has been suggested to introduce CoMP in the 3GPP Long Term Evolution (LTE/SAE) wireless communication system, but it should also be noted that CoMP is also applicable for other wireless communication systems, such as, for example, WiMax.
Although it is desired to build large CoMP cells of cooperating cells in order to minimize cell border effects that results in a worse user bit rate, cells in the network must be sub-divided into groups of cooperating cells in order to keep computation complexity at reasonable levels. However, the sub-division or formation of these groups of cooperating cells, that is, CoMP cells, can pose a very difficult task.
Besides being able to be based on a numerous different physical properties, such as for example, geographical proximity, radio wave propagation environment, traffic distributions and/or using neighboring-cell relations, including mobility information, such as handover statistics, the formation of a CoMP cell of cooperating cells also implies an increased level of hardware processing and backhaul capacity as compared to conventionally deployed non-cooperative wireless communication networks. The reasons for this increase include, for example, more complex deployment scenarios with differently sized cells, sub-cells, etc., as well as the increased higher grade of coordination between the cells on a shorter time scale.
Due to this inherent trade-off between an increased number of cells included in a CoMP cell of cooperating cells and increased complexity, a problem that may be experienced in forming CoMP cells of cooperating cells is that the CoMP cells of cooperating cells do not show the capacity or coverage performance as expected from their cooperating cell size.